Wireless systems in the cellular context are currently being implemented using fourth generation (4G) standards. These 4G standards include Long Term Evolution (LTE) standards developed by the 3G Partnership Project (3GPP). LTE cellular systems make use of an Internet protocol (IP) based packet core referred to as Evolved Packet Core (EPC). The EPC interconnects multiple base stations within the system. A given base station, also referred to as an evolved Node B (eNB), communicates over an air interface with multiple user terminals. Individual user terminals are also referred to as user equipment (UE).
The air interface between an eNB and UE in an LTE cellular system includes a variety of uplink and downlink channels. See, for example, 3GPP TS 36.211, V9.1.0, 3rd Generation Partnership Project Technical Specification, Group Radio Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA), Physical Channels and Modulation (Release 9), March 2010, which is incorporated by reference herein. One such channel is a downlink hybrid automatic repeat request (ARQ) channel referred to as PHICH (“Physical Hybrid ARQ Indicator Channel”).
In conventional PHICH processing, hybrid ARQ indicator (HI) codewords from a given PHICH group are each modulated, then subject to spreading and scrambling operations, then mapped onto a number of layers, and then precoded. The precoded layers from multiple PHICH codewords are then combined in a PHICH symbol combiner. Each PHICH group can hold up to eight codewords. Additional details regarding these and other conventional PHICH processing operations can be found in Section 6.9 of the above-cited 3GPP TS 36.211 document, at pages 57-61.
LTE system channels such as PHICH are subject to strict latency requirements. This can unduly increase the memory and computational requirements of the base station, leading to higher costs and increased power consumption.